1. AP Biology 2004-2005 Chapter 26. Origin of Life

2. AP Biology 2004-2005 The historical tree of life can be documented with evidence. The Origin of Life on Earth is another story…

3. AP Biology 2004-2005 Origin of Life hypothesis  Abiotic synthesis of organic molecules  amino acids & nucleotides  Building polymers  joining molecules into polymers  proteins & nucleic acids  Protobionts  packaging polymers into membrane- bound droplets  maintain internal chemistry  Origin of self-replicating molecules  makes inheritance possible

4. AP Biology 2004-2005 Conditions on early Earth  Reducing atmosphere  electron-adding  water vapor, CO 2, nitrogen, NO x, CH 4, NH 3, H 2, H 2 S  Energy source  lightning, UV radiation, volcanic What ’ s missing from that atmosphere?!

5. AP Biology 2004-2005 Abiotic synthesis  Testable hypothesis  1920 Oparin & Haldane propose reducing atmosphere hypothesis  1953 Miller & Urey test the hypothesis

6. AP Biology 2004-2005 Stanley Miller University of Chicago yielded amino acids hydrocarbons N bases other organic molecules

7. AP Biology 2004-2005 Protobionts  Life  reproduction & metabolism

8. AP Biology 2004-2005 RNA world  RNA is likely first genetic material  multi-functional molecule  codes information  enzyme functions  ribozymes  replication  regulatory molecule  transport molecule Dawn of natural selection

9. AP Biology 2004-2005 Key Events in Origin of Life  Key events in evolutionary history of life on Earth  life originated 3.5–4.0 bya

10. AP Biology 2004-2005 Prokaryotes  Prokaryotes dominated life on Earth from 3.5–2.0 bya 3.5 billion year old fossil of bacteria modern bacteria

11. AP Biology 2004-2005 Stromatolites fossilized mats of prokaryotes resemble modern microbial colonies Lynn Margulis

12. AP Biology 2004-2005 Oxygen atmosphere  Oxygen begins to accumulate 2.7 bya  photosynthetic bacteria  cyanobacteria (blue-green algae)  reducing  oxidizing atmosphere  corrosive  banded iron in rocks = rusting

13. AP Biology 2004-2005 Endosymbiosis  Evolution of eukaryotes  membrane bound organelles = 2.1 bya

14. AP Biology 2004-2005 Cambrian explosion  543 mya  within 10–20 million years most of the major phyla of animals appear in fossil record

15. AP Biology 2004-2005

16. AP Biology 2004-2005

17. AP Biology 2004-2005 Diversity of life & periods of mass extinction

18. AP Biology 2004-2005 The Chicxulub impact crater in the Caribbean Sea near the Yucatan Peninsula of Mexico indicates an asteroid or comet struck the earth and changed conditions 65 million years ago

19. AP Biology 2004-2005 Early mammal evolution  125 mya mammals began to radiate out & fill niches

20. AP Biology 2004-2005 Classification  Linnaeus used structural similarity  1969 Robert Whittaker devised 5 Kingdom system  Monera  Protista  Plantae  Fungi  Animalia

21. AP Biology 2004-2005 Re-Classifying Life  New groupings  molecular data challenges 5 Kingdoms  Monera is too diverse  2 distinct lineages of prokaryotes  Protists are too diverse

22. AP Biology 2004-2005 3 Domain system  Super Kingdoms  Bacteria  Archaea  extremophiles = live in extreme environments  Eukarya  eukaryotes

23. AP Biology 2004-2005 BacteriaArchae- bacteria AnimaliaFungiProtistaPlantae 4500 4000 3500 3000 2500 2000 500 1500 0 1000 Formation of earth Molten- hot surface of earth becomes somewhat cooler Oldest definite fossils of prokaryotes Appearance of oxygen in atmosphere Oldest definite fossils of eukaryotes First multicellular organisms Appearance of animals and land plants Colonization of land by animals Paleozoic Mesozoic Cenozoic Millions of years ago ARCHEAN PRECAMBRIAN PROTEROZOIC PHANEROZOC

24. AP Biology 2004-2005 Kingdom Protista Kingdom Fungi Kingdom Plantae Kingdom Animalia Kingdom Archaebacteria Kingdom Bacteria

25. AP Biology 2005-2006 Any Questions??